Do I really need a lightened flywheel?

topcatcustom · Post by **topcatcustom** » Wed Oct 08, 2008 5:21 pm

I'm now thinking that I dont need to be able to rev that little bit faster with a lighter fly as its a SC 4l RV8 (maybe with a little nos shot) in a little mx5 and I'm thinking it it revs too freely it will just light up the rears a bit too easily (as the car is so light), what do you lot think?!

JP. · Post by **JP.** » Wed Oct 08, 2008 6:00 pm

Looking over your previous posts, the answer is simple....No you don't if you want torque from low down. The flywheel helps generate torque, the lighter it is, the less it helps.

r2d2hp · Post by **r2d2hp** » Wed Oct 08, 2008 8:35 pm

You do not loose torque when using a lighter flywheel.

There is a very good explanation on this forum >> http://hondaswap.com/engine-building/li ... rque-9622/

Post by **Rossco** » Thu Oct 09, 2008 7:08 am

r2d2hp wrote:You do not loose torque when using a lighter flywheel.

There is a very good explanation on this forum >> http://hondaswap.com/engine-building/li ... rque-9622/

Correct but you do have less stored energy in the flywheel which means pulling away needs more rpm

sidecar · Post by **sidecar** » Thu Oct 09, 2008 7:08 am

r2d2hp wrote:You do not loose torque when using a lighter flywheel.

There is a very good explanation on this forum >> http://hondaswap.com/engine-building/li ... rque-9622/

I agree that you don't lose torque but I did not have a clue how to explain it! Your link does that very well!

In A.Bells book on 4 stroke lumps he states that reducing the rotational mass of the engine does in fact increase BHP during the transiant exceleration phase of an engine. (i.e. As the car is pulling up though the revs). Well, it might not be an "actual" increase in BHP but that's how the dyno see's it, the car will excelerate faster. At steady state revs there is no increase in BHP. (i.e no increase at peak revs or any other revs if the revs are held constant).

BHP being a function of torque.

The down side is as mentioned, there is less stored energy so the engine is more prone to bog or stall, and this can effect the tickover too.

Pete

chodjinn · Post by **chodjinn** » Thu Oct 09, 2008 7:13 am

bear in mind the car is an mx5 so its not gonna have much trouble pulling away. Get a lightened flywheel mate, i've got a silly ultralight alu one which is half the weight of my previous lightened flywheel, and that was amazing in the 'B!!

topcatcustom · Post by **topcatcustom** » Thu Oct 09, 2008 8:34 am

Good link! Kk so a lightened one would be nice- but that doesnt mean I am likely to find one which I can afford very soon!!!

chodjinn · Post by **chodjinn** » Thu Oct 09, 2008 10:47 am

Well FYI my flywheel and AP twin clutch cost me 400 beer tokens about 18mths ago. About 4-6 mths ago pretty much the same package came up on ebay and went for about 250, which is a bargain. Wait long enough and you can get what you want!

topcatcustom · Post by **topcatcustom** » Thu Oct 09, 2008 11:14 am

chodjinn wrote:Well FYI my flywheel and AP twin clutch cost me 400 beer tokens about 18mths ago. About 4-6 mths ago pretty much the same package came up on ebay and went for about 250, which is a bargain. Wait long enough and you can get what you want!

I do keep looking! Will using a lightened flywheel exaggerate the factory not-quite-balance of the crank in any way? (meaning the heavy spinning std one probably smoothes out discrepancies a little)

chodjinn · Post by **chodjinn** » Thu Oct 09, 2008 11:59 am

Its worth spending £150 or so to get the rotating assembly balanced. It's pretty much a no-brainer given the notoriety of Rover castings lol!!! As for feeling the affect, I doubt it very much because the heavier a spinning item the more rotational weight it will have, so if anything a lighter flywheel will reduce the 'vibration effects' if there are any. dont take my word for it.

FYI the clutch/flywheel package I have I estimate to cost close to £1k brand new (£600 clutch, £400 flywheel), so defo worth shopping round!!! The flywheel I have is actually shown on the V8D website, but they dont sell them and I still haven't found out who made mine. I know it came out of a TVR race car though, so maybe try John Eales for info.

DrDeAtH · Post by **DrDeAtH** » Thu Oct 09, 2008 4:54 pm

also add in a couple of quid for a dictionary...

it is
ACCELERATION

chodjinn · Post by **chodjinn** » Thu Oct 09, 2008 5:22 pm

he can buy you some manners while he's at it lol.

sidecar · Post by **sidecar** » Thu Oct 09, 2008 5:41 pm

DrDeAtH wrote:also add in a couple of quid for a dictionary...

it is
ACCELERATION

Nobody bothers to correct another forum contributors spelling mistakes, it's not the point of a forum. (Unless it's a spelling forum). Maybe you'll learn that when you're less "wet behind the ears"

Mark · Post by **Mark** » Thu Oct 09, 2008 7:55 pm

What's a 'sensible' weight for a V8 flywheel on a European size car ?

I made mine at work and it's 24 lbs but a much smaller diameter than a stock V8 flywheel so has less inertia.

Any views on if it needs to be lighter ?

Cheers

Mark

topcatcustom · Post by **topcatcustom** » Thu Oct 09, 2008 8:01 pm

sidecar wrote:
DrDeAtH wrote:also add in a couple of quid for a dictionary...

it is
ACCELERATION

Nobody bothers to correct another forum contributors spelling mistakes, it's not the point of a forum. (Unless it's a spelling forum). Maybe you'll learn that when you're less "wet behind the ears"

Sidecar you forgot your full stop at the end!!!